try_this.php

<?php

use Psr\Http\Message\ServerRequestInterface;
use React\Http\Message\Response;
use React\Promise\Deferred;

require __DIR__ . '/vendor/autoload.php';

$loop = React\EventLoop\Factory::create();

$server = new React\Http\Server($loop, static function (ServerRequestInterface $request) use ($loop) {
    $duration = 1.5;
    echo sprintf("Sleeping for %F\n", $duration);
    $promise = new Deferred();
    $loop->addTimer(1.5, function () use ($promise) {
        echo "After Sleep";
        $promise->resolve(new Response(200, [], 'Some reponse'));
    });
    

    return $promise;
});

$socket = new React\Socket\Server('127.0.0.1:8080', $loop);
echo "Server running at http://127.0.0.1:8080\n";

$server->listen($socket);
$loop->run();